It is a monoclonal antibody that binds to CD52, a protein present on the surface of mature lymphocytes, but not on the stem cells from which these lymphocytes are derived. After treatment with alemtuzumab, these CD52-bearing lymphocytes are targeted for destruction.

Alemtuzumab is used as second-line therapy for CLL. It was approved by the US Food and Drug Administration for CLL patients who have been treated with alkylating agents and who have failed fludarabine therapy. It has been approved by Health Canada for the same indication, and additionally for CLL patients who have not had any previous therapies.

(Mab)Campath was withdrawn from the markets in the US and Europe in 2012 to prepare for a higher-priced relaunch of Lemtrada aimed at multiple sclerosis.[1]

Alemtuzumab is indicated for the treatment of B-cell chronic lymphocytic leukemia (B-CLL) in patients who have been treated with alkylating agents and who have failed fludarabine therapy. It is an unconjugated antibody, thought to work via the activation of antibody-dependent cell-mediated cytotoxicity (ADCC).[2]

In September 2013 alemtuzumab was approved for first-line use in the EU.

In November 2013, the US FDA issued a comprehensive briefing on alemtuzumab for an agency review meeting. The document highlighted numerous serious safety and efficacy concerns, including substantial doubts about the adequacy of relevant clinical trials.[4] In December 2013, the US FDA indicated that the Lemtrada application is not ready for approval, due to lack of evidence from "adequate and well-controlled studies" that demonstrate that the benefits of the drug outweigh the risks.[5] The CEO of Genzyme, David Meeker, strongly disagreed with this decision and indicated that the company would file an appeal.

On December 1, 2014 the first treatments with Lemtrada (or alemtuzumab) were administered to the first patients outside clinical trials. Dr. Christopher LaGanke was the attending physician and was also instrumental in having the FDA reconsider the approval.[7]

Alemtuzumab is contraindicated in patients who have active systemic infections, underlying immunodeficiency (e.g., seropositive for HIV), or known Type I hypersensitivity or anaphylactic reactions to the substance.

The origins of alemtuzumab date back to Campath-1 which was derived from the rat antibodies raised against human lymphocyte proteins by Herman Waldmann and colleagues in 1983.[12] The name "Campath" derives from the pathology department of Cambridge University.

Initially, Campath-1 was not ideal for therapy because patients could, in theory, react against the foreign rat protein determinants of the antibody. To circumvent this problem, Greg Winter and his colleagues humanised Campath-1, by extracting the hypervariable loops that had specificity for CD52 and grafting them onto a human antibody framework. This became known as Campath-1H and serves as the basis for alemtuzumab.[13]

While alemtuzumab started life as a laboratory tool for understanding the immune system, within a short time it was clinically investigated for use to improve the success of bone marrow transplants and as a treatment for leukaemia, lymphoma, vasculitis, organ transplants, rheumatoid arthritis and multiple sclerosis.[14]

Campath as medication was first approved for B-cell chronic lymphocytic leukemia in 2001. It is marketed by Genzyme, which acquired the world-wide rights from Bayer AG in 2009. Genzyme was bought by Sanofi in 2011. In August/September 2012 Campath was withdrawn from the markets in the US and Europe. This was done to prevent off-label use of the drug to treat multiple sclerosis and to prepare for a relaunch under the trade name Lemtrada, with a different dosage aimed at multiple sclerosis treatment, this is expected to be much higher-priced.[1]

Bayer reserves the right to co promote Lemtrada for 5 years, with the option to renew for an additional five years.

In February 2011, Sanofi-Aventis, since renamed Sanofi, acquired Genzyme, the manufacturer of alemtuzumab.[15] The acquisition was delayed by a dispute between the two companies regarding the value of alemtuzumab. The dispute was settled by the issuance of Contingent Value Rights, a type of stock warrant which pays a dividend only if alemtuzumab reaches certain sales targets. The contingent value rights (CVR) trade on the NASDAQ-GM market with the ticker symbol GCVRZ.

In August 2012, Genzyme surrendered the licence for all presentations of alemtuzumab,[16] pending regulatory approval to re-introduce it as a treatment for multiple sclerosis. Concerns[17] that Genzyme would later bring to market the same product at a much higher price proved correct.